#2339: Template Haskell reification with mkName doesn't work right
---------------------------------+------------------------------------------
Reporter: simonpj | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Template Haskell | Version: 6.8.2
Severity: normal | Keywords:
Difficulty: Unknown | Testcase:
Architecture: Unknown | Os: Unknown
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Marc Weber writes: this doesn't work:
{{{
-- packages: template-haskell
{-# OPTIONS_GHC -XTemplateHaskell #-}
module Main where
import Language.Haskell.TH
data A a = A a
type C = A Int
data ABC = ABC Int
$(do
a <- reify $ mkName "C"
report False $ show a
return []
)
main = print ""
}}}
Produces output
{{{
|| [1 of 1] Compiling Main ( test.hs, test.o )
||
test.hs|1| `C' is not in scope at a reify
}}}
Using `mkName "A"` results in
{{{
test.hs|1 error|
|| DataConI Main.A (ForallT [a_1627391370] [] (AppT (AppT ArrowT (VarT
a_1627391370)) (AppT (ConT Main.A) (VarT a_1627391370)))) Main.A (Fixity 9
InfixL)
}}}
as expected
Why do I need it?
I'd like to implement kind of very basic relational data representation
the way `IxSet` is doing it but without dynamics..
It will look like this:
{{{
type CDs = Table (Autoinc, Artist, Title, Year) -- col types
(Artist, Title, Year) -- keys
() -- is detail of
type Tracks = Table (Autoinc, Title, RecordingDate)
(Title, RecordingDate)
(CDs)
$(mkDB ["CDs","Tracks"])
}}}
To be able to automatically derive
{{{
insert{CDs,Tracks}
delete{CDs,Tracks}
update{CDs,Tracks}
}}}
functions I need to get information about those types.. Is this
possible?
Thanks
Marc Weber
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2339>
GHC <http://www.haskell.org/ghc/>
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